Soil Moisture Sensitivity Analysis in the Upper Missouri River Basin

The Upper Missouri River Basin (UMRB) spans portions of five states—Montana, North Dakota, South Dakota, Wyoming, and Nebraska—and is a key region for agricultural production in the United States. In response to severe drought and flood events in the UMRB between 2011 and 2019, the Infrastructure Investment and Jobs Act provided funding to improve water monitoring in the region. The UMRB Data Value Study, led by NOAA’s National Integrated Drought Information System (NIDIS), is the assessment element of this multi-component, multi-agency project. 

Led by the Ohio State University, the Soil Moisture Sensitivity Analysis in the Upper Missouri River Basin (Sensitivity Analysis) project is a component of the Data Value Study. The research team tested the hypothetical outcome of increasing the UMRB monitoring network from 78 to 540 soil moisture monitoring stations, modeling how the planned expansion would impact the representation of drought or unusually wet conditions. This project found increasing network density provides more skillful representation of modeled soil moisture mapping and could contribute to the ability to better characterize current conditions for decision-makers. 

A Test Case for Potential Economic Ramifications of Expanded Soil Moisture Monitoring

The Sensitivity Analysis used a hypothetical case study to test the accuracy of the UMRB soil moisture network’s representation of basin-wide soil moisture conditions using the 2017 Water Year, which saw severe drought in the region. Specifically, this project looked at the impact of station density on: 

1. Representation of drought conditions in summer 2017

2. Representation of wetter-than-normal events in fall 2017

3. Potential economic impacts of a more skillful drought representation, driven by improved soil moisture information and products.

This study used point-specific data from the North American Land Data Assimilation System (NLDAS-2) to represent in situ data from the proposed new UMRB station locations. The researchers found the products generated using the expanded network had greater skill in drought classification, compared to the soil moisture products generated using the original, sparser network. Characterization of soil condition also improved for pluvial events (when soils are wetter than normal, with the potential to contribute to flooding). These findings suggest expanded monitoring networks could better support decision-making around hydrologic events.

Additionally, the Sensitivity Analysis project ran a thought exercise to consider the scale of potential economic impacts associated with improved skill in drought representation. The researchers used the methodology associated with the Livestock Forage Disaster Program (LFP) to calculate hypothetical payments for drought damages—if drought classifications were based solely on soil moisture information from NLDAS-2. (In reality, LFP payments are based on more than just soil moisture.) This test case indicated expanding the network to 540 stations improved accuracy of hypothetical payouts on the scale of hundreds of millions of dollars for the UMRB for this drought event.

Because this project used soil moisture as the sole indicator of drought, the findings from the Sensitivity Analysis cannot be used in a one-to-one comparison with the U.S. Drought Monitor or actual LFP payments. The U.S. Drought Monitor uses a consensus-based approach and considers many indicators to generate drought classifications, while this study classified drought based solely on soil moisture conditions. However, findings from the Sensitivity Analysis indicate more targeted and skillful monitoring could improve representation of drought and pluvial events for products that include soil moisture information. It also suggests expanded soil moisture networks may support future improvements to the next generation of drought classification products and tools.

For more information, please contact Elise Osenga (elise.osenga@noaa.gov).